1. Field of the Invention
The present invention relates to a temperature sensor probe, and more specifically relates to a temperature sensor probe that has a powder fluorescent substance.
2. Description of the Related Art
Fluorescent type temperature sensors that use fluorescent substances are widely used as temperature sensors (Japanese Laid-Open Patent Application No. 2002-71473). In a fluorescent type temperature sensor, the temperature is measured using a fluorescent substance that changes fluorescence characteristics depending on temperature. Concretely, excitation light from a light source is irradiated on the fluorescent substance, and the fluorescence produced by the fluorescent is detected. Then, the temperature is measured based on the changes in fluorescence characteristics such as fluorescence lifetime.
A fluorescent material containing a fluorescent substance is arranged at the tip of optical fibers. Then, the excitation light irradiated from a light source falls incident on the fluorescent substance through the optical fibers. Moreover, the fluorescent light generated by the fluorescent substance is detected by an optical sensor through the optical fibers. Powder fluorescent substance may be used in temperature sensor probes using this kind of temperature sensor. Further, it has been disclosed in a patent that the particle size of the powder of the fluorescent substance is 40 μm or less (Japanese Laid-Open Patent Application No. Hei 2-290518).
Nonetheless, in the probe of Japanese Laid-Open Patent Application No. Hei 2-290518 there is the problem that because of the small particle size sufficient intensity of fluorescence cannot be obtained. For example, even if each individual particle is transparent, the fine particles fit together, pile up and form layers. As indicated in FIG. 7, if the particle size of the fluorescent substance is small, the excitation light is randomly reflected in non-specific directions by the particles, and transparency is lost. In FIG. 7, the solid arrows indicate the propagation routes of incident light, and the broken arrows indicate the propagation routes of fluorescent light. The excitation light irradiated out from the optical fibers is reflected near the surface without being delivered deep into the fluorescent substance. Therefore, because the only the surface of fluorescent substance fluoresces, sufficient intensity of fluorescence cannot be obtained. If sufficient intensity of fluorescence cannot be obtained, then the intensity of fluorescence to noise in the detection route is small, and the calculated measurement results ill fluctuate with every reading. Moreover, unless the particle size is regulated, the fluorescence lifetime will fluctuate depending on the internal stress of the powder, and measurements will be different for every powder. In this way, convention temperature sensor probes had the problems of not being able to obtain sufficient intensity of fluorescence and of difficulty in conducting stable measurements.
Attempting to resolve these kinds of problems, an object of the present invention is to present a temperature sensor probe that can conduct stable measurements, and the manufacturing method thereof.